The present invention is directed to a device for the controlled dispensation of a plastic mass or substance out of cartridges. The device includes a hollow cylinder containing a piston slidably displaceable through the cylinder with a pusher rod secured to the piston and means for driving the piston and pusher rod by a pressure medium in the cylinder. A pressure support mounts the cartridges on one end of the cylinder.
Devices of the above-mentioned type are generally used in the construction industry for filling-in gaps and cracks, or for bonding or anchoring fastening elements in boreholes formed in a receiving structure. Accordingly, a plastic material formed of a single or multi-componenet system is used which is hardenable or remains in the elastic state after being dispensed.
In most of the previously known devices for dispensing such substances, the dispensing force is supplied manually through a mechanism actuated by a lever or handle. When such substances are dispensed at low temperatures they can have a high viscosity such that the force required to dispense the substance can not be provided manually. This characteristic provides a considerable disadvantage if fastening elements of large dimensions are to be anchored and large amounts of the anchoring substance are required. Accordingly, it has been known to provide such devices where the driving force is supplied by an external source. Generally, compressed air has been used as the external source,since it is not a dangerous substance and often is available at construction sites.
In manually operated devices as well as those operated by an external source, the pusher rod effecting the displacement of the substance out of the cartridge must be retracted into its original starting position to replace the cartridge. Such replacement does not afford any significant problem in manually operated devices, since the pusher rods are arranged so that they project rearwardly from the housing in which the drive mechanism is positioned even when the pusher rod is displaced through the cartridges. After a stop member for the pusher rod is released, the pusher rods can be pulled rearwardly into the original starting position. If the dispensing device utilizes an external source of energy, the return of the pusher rods into the starting position is considerably more complicated. In one known dispensing device, the pusher rods are not directly accessible from the side. As a result, special tools are required for returning the pusher rods to the starting position.
In another known dispensing device, the piston can be moved by the pressure medium in the dispensing direction as well as in the opposite direction. Such an arrangement, however, requires additional connecting lines and a complicated reversing valve. Accordingly, such a device is more expensive and more prone to malfunction.